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From Dave Newton <davelnew...@gmail.com>
Subject Re: Customizing validation
Date Tue, 29 Nov 2011 01:01:45 GMT
If the goal is to execute validations based on arbitrary preconditions (I
missed the original req) the *easiest* thing to do might be to just
extend/usurp the existing validation interceptor to do that precondition
check.

d.

On Mon, Nov 28, 2011 at 7:58 PM, Li Ying <liying.cn.2010@gmail.com> wrote:

> Looks like you want some pre-condition check before the validation.
> If and only if the pre-condition is true, the validation will be executed.
>
> I did the same thing several years ago.
>
> There are 2 solution I tried:
> (A)Inherit all the struts2 bundled validators, add some pre-condition
> check code,
> if and only if the pre-condition is true, invoke the method of the
> base class. The base class (struts2 bundled validators) will do the
> left work.
>
> BTW, the pre-condition should be passed into the validators via
> <param>, so the validators will not include any business logic and
> they can be reused.
> And since your pre-condition is a session attribute, I think you can
> check it's value by OGNL expression. I am not very sure for this. If
> you can not access session attribute via OGNL, maybe you need a
> [getCountry] method in your action class, so the OGNL can retrieve the
> value.
>
> You don't need reinvent the whole wheels, but extend the existed wheels.
>
> Source code like:
> public class XXXValidatorEx extends XXXValidator {
>     private String condition;  // here is the pre-condition in OGNL
>
>     public getCondition(); // omitted
>     public setCondition(); // omitted
>
>     private boolean evaluateCondition(){
>         // omitted
>         // you can read the code of [ExpressionValidator] and
> [FieldValidatorSupport], to learn how to evaluate an OGNL expression.
>     }
>
>     public void validate(Object object) {
>           boolean result = this.evaluateCondition();
>           if (result ) {
>               super.validate(object);
>           }
>     }
> }
>
> There are about one dozen bundled validators, and the source code of
> the inherited validators will be almost 100% same (only except the
> class name and the base class name).
> This will be a little ugly, but we have no choice, because Java don't
> support multi-inherit or interface-delegation.
> My choice was, generating all these source codes via FreeMarker, so I
> need maintenance only one template file, but not one dozen of class
> source codes.
>
>
> (B)The other solution is much lighter.
> No need the enhance the validator class, but express your
> pre-condition and your validation rule all by expression.
>
> like:
> <validator type="expression">
>     <param name="expression">(!pre-condition) or (check-rule)</param>
> </validator>
>
> This will be easy to do, but hard to use,
> because you must translate all the validation rules into some OGNL
> expression
>
>
>
> Anyway, I think the final and most beautiful solution should be,
> adding some [pre-condition checking] into the Struts2 bundled
> validators themselves.
> But this is out of our control, hope the developers of Struts2 can here
> this.
>
>
>
> 2011/11/28 Jyothrilinga Rao <jyothril@gmail.com>:
> > Thanks Li Ying,
> > I got some information from
> >
> http://today.java.net/pub/a/today/2006/01/19/webwork-validation.html?page=3#custom-validators
> > but I do not want to reinvent the wheel (basically avoid coding my
> > validation logic in java code). If I
> > could have my <actionClass>-validation.xml structured as
> >
> > <validators>
> > *<country name="USA">
> > *  <!-- Field Validators for email field -->
> >  <field name="email">
> >      <field-validator type="required" short-circuit="true">
> >          <message>You must enter a value for email.</message>
> >      </field-validator>
> >      <field-validator type="email" short-circuit="true">
> >          <message>Not a valid e-mail.</message>
> >      </field-validator>
> >  </field>
> >  <!-- Plain Validator 1 -->
> >  <validator type="expression">
> >      <param name="expression">email.equals(email2)</param>
> >      <message>Email not the same as email2</message>
> >  </validator>
> >  *</country>*
> > *<country name="AUSTRIA">
> > *   <!-- Field Validators for email2 field -->
> >  <field name="email2">
> >     <field-validator type="email">
> >          <message>Not a valid e-mail2.</message>
> >      </field-validator>
> >  </field>
> >  <!-- Plain Validator 2 -->
> >  <validator type="expression" short-circuit="true">
> >      <param name="expression">email.startsWith('mark')</param>
> >      <message>Email does not start with mark</message>
> >  </validator>
> > *</country>*
> > </validators>
> >
> > I am looking for something like a wrapper on existing bundled validators.
> > Is it possible.
> >
> > Regards,
> > JK.
>
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